Surfaces are universal and are widely used in various contexts in daily living. The ability to control chemical or physical properties of a surface, such as hydrophobicity, antibacterial nature, antifouling nature, anti-icing property, and biocompatibility can be crucial in many applications. To introduce or modify a specific surface property has been the study in industry for decades and can be explored by incorporating selected elements or functional groups onto a surface. A classic example is the mussel-inspired polydopamine coating in which dopamine has been polymerized in basic aqueous solutions, resulting in a polydopamine coating on various surfaces immersed within the basic aqueous solutions. The polydopamine coating could, in turn, be reacted with thiols, amines, or metal ions to introduce further functionalities, offering a simple and versatile strategy for surface modification for many materials.
In such manner, it has been desired for some time to modify surfaces of a substrate such as a glass or polymeric materials so that they have various surface properties for industrial applications. For example, such a surface can be defined by the level of hydrophobicity or hydrophilicity depending upon the value of the water contact angle. A surface having a water contact angle that is greater than 90° is generally considered hydrophobic while a surface having a water contact angle less than 90° is generally considered hydrophilic. In practice, two types of water contact angle values can be considered: static and dynamic. Static water contact angles (θst) are obtained by sessile drop measurements where a drop of water is deposited on the surface and the value is measured using a goniometer or specialized software. Dynamic contact angles are non-equilibrium contact angles and are measured both during the growth and shrinkage of a water droplet. The difference between these two measurements is defined as contact angle hysteresis.
U.S. Patent Application Publication 2015/0344652 (Linxian et al.) describes a method for modifying or producing super hydrophobic surfaces having a water contact angle greater than 150° that can be modified to produce surface patterns having different chemical functionalities, for example superhydrophilic-super hydrophobic surfaces for various industrial purposes. Such patterns can be generated using the known “click” chemical reactions that have been used and reviewed in various publications for several decades (for example, see summary Mostegel et al., Journal of Materials Chemistry B, 3(21), pp. 4431-4438, 2015; and Davis et al., Langmuir 30, 4427-4433, 2014; and references cited in both publications). However, surfaces that are merely hydrophobic and not superhydrophobic (a water contact angle less than 150° but greater than 90°) have not been described for producing dewetting patterns. Such a technique would be desirable because achieving superhydrophobicity often requires more process-intensive techniques and multi-step processing that includes both chemical and physical means of hydrophobicity, such as chemical repulsion and surface roughening.
U.S. Patent Application Publication 2013/0040070 (Jung et al.) describes a method for forming a microstructure pattern using double-dewetting edge lithography in which a photoresist pattern is formed on a hydrophilic substrate, followed by assembling a monolayer for example of a silane or thiol group, and multiple selective dewetting steps to leave a desired solute pattern.
U.S. Pat. No. 7,851,344 (Kugler et al.) describes the fabrication of microelectronic components by depositing electronically functional materials onto a substrate that possesses a wetting contrast. The wetting contrast areas are created by different plasma treatments of the substrate.
Despite the advances in the art in this technology, there is a need for further improvement. For example, there is a need for a means to provide fine lines in patterns in a rapid and consistent manner on highly transparent substrates. There is also a need to improve the adhesion of applied “inks” to either hydrophilic or hydrophobic regions so that the applied ink can be used for further operations without physical failures in either type of region. There is also a need for aligning patterns on both supporting surfaces of substrate (for example, planar objects).